A common problem in cosmetic compositions has been the effective delivery of actives to the skin. Since cosmetic compositions often have numerous ingredients to make it cosmetically acceptable, the amount of active is often diluted. Moreover, the presence of other ingredients can impede the amount of active that is actually delivered within the skin. Even if ingredients in the cosmetic compositions do not impede effective delivery of the active to the skin, the active may fail to successfully adhere to the skin to deliver essential actives to the skin.
Moreover, many actives are unstable in cosmetic vehicles. For example, Polyphenone E, the active component of Green Tea, drastically discolors and loses activity when incorporated into an emulsion containing water. Polyphenone E is known to possess potent anti-tyrosinase activity. Skin pigmentation and tanning are related to the amount of melanin in epidermal melanosomes. In the melanosomes, the enzyme tyrosinase oxidizes tyrosine and the resulting intermediate compounds polymerize to form the brown-black melanin pigment. The formation of melanin is believed to be a defensive mechanism in humans which protects their skin from harmful ultraviolet rays. However, the excessive formation of melanin following prolonged sun exposure or due to disorders of epidermal melanin units is responsible for melasma, ephelides, and pigmented cosmetic dermatitis. Although the precise mechanism of excessive melanin formation has not been fully elucidated, the activation of tyrosinase appears to be a significant factor. Thus, the development of chemical agents capable of modulating the enzyme activity of tyrosinase would have considerable value for the control of the above-noted undesirable skin conditions. See U.S. Pat. No. 5,466,718.
Hinokitiol is a bacterial fungicide that is known to have anti-irritant, anti-microbial and skin lightening properties. However, when Hinokitiol is incorporated into an emulsion, the Hinokitiol develops a strong, unpleasant odor and discolors the emulsion to a yellowish-brown color upon storage.
Retinoids constitute a large group of synthetic and naturally occurring compounds related to retinol, the vitamin A alcohol. In mammals, retinoids fulfill essential roles, including maintenance of epithelial cells. However, retinoids are known to be chemically unstable and nearly insoluble in water. Therefore, retinoids are difficult to incorporate into cosmetic compositions.
Other examples include vitamins that are unstable in cosmetic compositions. For example, vitamin C has many skin benefits for the skin, including whitening and stimulating collagen synthesis. As is known in the art, collagen synthesis makes the skin stronger, which helps reduce lines and wrinkles. However, vitamin C is known to be very unstable when exposed to water, oxygen and light and therefore loses its activity and drastically discolors.
Therefore, there continues to be a need for a topical delivery system that is effective in delivering an unstable active to the skin while creating a stable environment for that active.